Nothing more far from reality! Efficiency and performance are related by
Performance = Efficiency x Power
Thus if you double the efficiency, then you double the performance at same power consumption levels. This is true either if you are considering a mobile 1W device or if you are considering a HEDT 300W device.
Moreover, HEDT products are not fabricated in a vacuum, but are derived from rest of products of the company. E.g. your FX-8350 is derived from a design aimed at servers and supercomputers. Servers and supercomputers don't consume 1000W; a top supercomputer can consume 20MW and the electricity costs are about so big, thus efficiency is even more important.
AMD main failure on last years (pre-Rory) was to ignore efficiency as key metric and it was the reason why AMD almost lost the server, supercomputer, and laptop markets, and never enter the tablet/phone market, whereas survived on the desktop with low prices, which generated an enormous debt for the company, which itself generated the cancellation of many programs and the cut on R&D. The next figure is self-explicative
Luckily for us, the new management understands that efficiency is key and this is the reason why Papermaster gave the "25x20" talk
http://www.amd.com/en-us/press-releases/Pages/amd-accelerates-energy-2014jun19.aspx
http://www.amd.com/en-us/innovations/software-technologies/25x20
During the last Future of Compute conference, AMD has emphasized again the efficiency goal
The 25x20 goal means by 2020 you can have a HEDT product of 200W which will be about
25x more faster than current 200W products...